Hack saw blade



w. H. SHRTELL 1,899,212

Feb. 28, 1933- HAcx sAw BLADE Filed Aug. 22', 1951 @d mv INVENTOR oRNEY i Patented Feb. `28,11932);

11.2 ,SHOBTELn OEGREENFIELD, -iMASS; icirusnrrcls,IAssreimm.. "roA` MILLS v Y .coMrANYgor-enEENFIELm MASSACHUSETTS; AcoRPoRAfrIoN 10F 4:unissaeizusa'r'is fr Harn;saw` :BLADE This invention relates-to improvements in saw blades and more particularly to improved i y i hack saw blades, ,wherein the enterin end of the blade,` i. e., the end, :which is first; rought into contact with the work, rovidedf with teethgso constructed as toresist re`a-kagee`ven` under thefseverest strains-to which they= are normally subjected. f

- An` object' of the invention is to provide a y l0 sawfhaving'teethA ofequalfpitcmii. e., angle" kofinclination.orrake, throughout butv pro-V vided at v,its enteringfendwith aseries of teeth of great'strengthfadapted to resist breakage when brought into contact with the work. i

. A further objectofrtli'e' invention is to profl i vide a vsaw 'blade 4having teethy of equal. chip clearance throughout ,butv provided at its en-U tering4 end `With aseries of `teeth ofgradul ally diminishingvdepth, adapted normally to engage thefwork* without breaking.v The term chip clearance, or Y chip clearance opening as used hereinshallbe understood as' meaning vthe distance betweenthe back of 5 one tooth von-the blade and "thecutting edge-fticle of manufacture possessing thefeatures, 35 properties andthe relation ofelements lwhichy will be exemplified inthe articlehereinafter described andthe scope yof the application of which Willl be indicated inthe claims.V`

,- Fora fuller understanding offthe'naturey 40 andfobjects of the invention, lreference should be had to the followingk detailed description y taken in1connection withrthe 'accompanying I, drawing,.in which: I. -f v Figgl 'isla side view of. a saw bladeembOdYIlg my; invention;

Fig. 2 is an enlarged fragmentary side View,

showing a portion of the teeth representative of the great majority ofteeth on the blade;

and

v '50. FigfS is a vievv similar to Fig.r-2, showing f strain placed upon them.,y y Variousattemptshave been a portion4 ofthe Series of "teeth withvwihich l the enteringendf ofthe blade is providedf p Saw blades are. ordinarily providedw'ithy relatively.coarsefteeth in order to kexpedite kthe cutting.l The'softer'i'thev stock to be cut,

thecoarserthe teeth are made. It has bee-1,1- found thatjwhere lsavv teeth are madeas largel and coarse as the type loflWork-requ'ires', there the' -teethare first brought into 4contact with the Work, for jthelarge, `coarse teeth do not ist is very considerable danger of breakage when have sufhcientstrengthto resist the sudden? edy this situation and 'saw bladeshave lbeen teeth of. fdili'erent character' fromthe i teeth *y found on the main partk of the blade, with the brought into contactwiththe "Work, and the -initialistrainsoit that contact absorbed byl teeth specifically designed t'ofovercom'e it.

made to rem- 'pkdeveloped with a Vrelativelys'hort series of i Vintent that these ymodified teeth shall first be ,7,

yFor example, a series of file-liketeeth,y

strong, but very ine,h`asfbeen suggested for usel on the entering end of lthe blade! Such a blade',- however, 'possesses' certain '-.distinct disadvantages; The fine teeth tend to :clog

bladeis lower.,l It has been also with chips andthe generalijeiiiciency of the suggested that series of blade Which'have the same pitch as themain provided With a relatively heavy backing so that a series'of broad teeth With'narrow chip se; yteethbeprovided at the entering end of the clearance openings is provided. `Teeth of this f kind are stronger,y at all points; except the base", than'fthe teeth on ythe' maink part ofthe saw, 'I but ithas been'foundthat breakage usually takes place at the base of theteeth and hence,'the disadvantage and loss of eiciency lincident to 'the narrowing of the chip clearance openings, is' not compensated for the i.. slight improvementiin strength se?" cured.` f'

Other-modiliedblades havebeensuggested butthey all possess certain disadvantages f which' impair thek eiiiciency ofthe blade.I

the feature of added strength in the? entering My :improved sawbla'de, While possessing ,y

of equal pitch throughout and ot equal chip clearance opening. VAdded strength is given to the teethrat the entering end of theblade by gradually diminishingrthe depth of the tooth as theentering end of the blade is reached..V In this way, the teeth are made progressively stronger toward the: entering end of the blade, so that the first tooth, i. e.,v

the one most likely to comeffirst into contact with the work, is strongest, and the teeth behind it on the bladel progressively weaker until a certain predetermined tooth depth is reached, after which the remainderof the teeth are of equal strength.

- In the accompanying drawing, 10 repre- Y sents a saw blade provided with the f usual openings, 11, at its ends, for adjustment to a hack saw frame. The blade -is provided throughout the greater portion of its length withaseries of teeth. 12, of uniform size and shape, shown in detailin Fig. 2.

In advance of this series of teeth and at the entering end of the blade, a series of teeth, 13,

is provided. These teeth. some of which are` shown in detail in Fig, differ from the, main body of teeth on the blade only in that the toothgdepthof theteeth 13 is gradually decreased from the standard tooth depth of the teeth 12, to a minimum on the entering tooth, asat14.-` l K V- The saw teeth are made so that the back 'of onetooth makes contact withithe face of Fig. 3 at 16and 17, and the arc itself .en-

larged, the tooth depth will be Vgradually decreased without affecting the pitch, the tooth angle or the chip clearancevopening. As the tooth depth is decreased, the teeth become progressively stronger, shorter and more sturdy. TheV added strength is ernbodied at the base where it -is most needed. By increasing thevsize of the arc 15V, the tooth depth can be decreased to any point desired without affecting the other characteristics of the tooth. A saw blade provided at its entering end witha series of teeth formedV in this manner is ecient,strong and easy to manufacture. It stands up well underthe strain Vof normal usage and possesses none of the disadvantages of othermodiiied blade sturdy teeth with shallow depth shall be first Abrought into contact with the Work and that suiiicient of these teeth shall be provided to smooth the work before the normally coarse teeth of the blade are brought into contact with it, so that there is little likelihood of breakage to any part of the blade.

v Since certain changes may be made in the above article and different embodiments of' the invention could bemad'e without departing from thescope thereof, it is intendedthat all matterl contained in the above description or shown in the accompanying drawing shall be interpreted asl illustrative and not in a limiting sense.

' It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention herein.- described and all statements of the scopeof the invention which as a matter of languagemight be said to fall therebetween.

Having described my invention, Vwhat I claim as new and desire to secure by Letters Patent, is:-`

1. A saw blade provided with teeth, all having substantially thesame pitch and chip clearance opening, a series ofsaid teeth at its entering; end having ,ishallower depths than the remainder of the teeth.` Y

2. A saw blade provided with teeth, all having substantiallyl the same pitch and chip clearance opening, a group of said teeth having a substantially uniform depth, and the remainder of said teeth having progressively shallower depths than said first-mentioned group. e

3. A saw blade provided with teeth, all havingsubstantially the same pitch and chip clearance opening, a series of said teeth being of .uniform strength, another series of said teeth, located at the enterng end of the blade, being progressively of less depth and stronger than theteeth in said first mentioned series.

4. A hack saw blade provided with teeth, all having substantially the same pitch and chip clearance opening, the teeth at its entering end being suiiciently shallow in depth to prevent` breakage when brought into contact with the work.

`5. A hack saw blade provided with teeth, all having substantially the same pitch and chip clearance opening,.the tooth at the entering end ofthe blade having the shallowest depth, the teeth adjacent thereto having progressively greater depths until a maximum tooth depth is reached, the remainder of the teeth all having; `substantially the desired maximum tooth depth.

. In testimony whereof I aiix my signature.

WILLIAM H. SHORTELL.

CERTIFICATE 0F CORRECTION.

Patent N0. 1,899,212. February 28, 1933.

WILLIAM H. SHRTELL.

lt is hereby cer'rified that the name of the assignee iii the above numbered.

paient was erroneously described und specified as "Mils Faiis Gonipm1y"\\'here as said name should have been described and specified as "Miiiers Fails GumpQ any," as shown by the records of assignments in this effige; aad that the said Letters Patent shouid be read with this correction therein their the same may conform to the record of the case in the Patent Office.

Signed and sealed this 25th day of April, A. D. i933.

. M..'Moore. (heal) Actmg Commissioner of Patents. 

